Purpose: High-intensity interval training (HIIT) is emerging as an effective and time-efficient exercise strategy for health promotion. However, most HIIT studies are conducted in laboratory settings and evidence regarding the efficacy of time-efficient "low-volume" HIIT is based mainly on demanding "all-out" protocols. Thus, the aim of this pilot study was to assess the feasibility and efficacy of two low-volume (≤ 30 min time-effort/week), non-all-out HIIT protocols, performed 2 ×/week over 8 weeks in a community-based fitness centre.
Methods: Thirty-four sedentary men and women were randomised to either 2 × 4-min HIIT (2 × 4-HIIT) or 5 × 1-min HIIT (5 × 1-HIIT) at 85-95% maximal heart rate (HRmax), or an active control group performing moderate-intensity continuous training (MICT, 76 min/week) at 65-75% HRmax.
Results: The exercise protocols were well tolerated and no adverse events occurred. 2 × 4-HIIT and 5 × 1-HIIT exhibited lower dropout rates (17 and 8 vs. 30%) than MICT. All training modes improved VO2max (2 × 4-HIIT: + 20%, P < 0.01; 5 × 1-HIIT: + 27%, P < 0.001; MICT: + 16%, P < 0.05), but the HIIT protocols required 60% less time commitment. Both HIIT protocols and MICT had positive impact on cholesterol profiles. Only 5 × 1-HIIT significantly improved waist circumference (P < 0.05) and subjective work ability (P < 0.05).
Conclusions: The present study indicates that low-volume HIIT can be feasibly implemented in a community-based setting. Moreover, our data suggest that practical (non-all-out) HIIT that requires as little as 30 min/week, either performed as 2 × 4-HIIT or 5 × 1-HIIT, may induce significant improvements in VO2max and cardiometabolic risk markers.
Keywords: Cardiometabolic health; Cardiorespiratory fitness; Feasibility; HIIT; Real-world setting; Time-efficient exercise.